William Edgar Geil (1865-1925), a famous U.S. traveler in the early 20th century and a member of the Royal Geographical Society. [1] In 1908, he completed a full-scale investigation of the Great Wall in China, and published the first monograph on the Great Wall in the world the following year. He was one of the most experienced travelers of his time. He visited China four times and wrote four monographs (Americans on the Yangtze River, Great Wall of China, Eighteen Provincial Capitals of China and Five Mountains of China).